This specification relates to optical communications.
Optical fiber amplifiers are commonly used in communication systems. Types of optical fiber amplifiers include Rare Earth Doped Fiber Amplifiers, for example, Erbium Doped Fiber Amplifiers (“EDFAs”). The optical fiber amplifiers are usually pumped by one or more light emitter diode (LEDs) or laser pump sources.
An erbium doped fiber (EDF) is a form of a single-mode fiber, having a core that is heavily doped with erbium. Conventional EDFA's include a pump laser that provides a pump light to the erbium doped fiber to provide amplification. For example, when pump light at 980 nm or 1480 nm is injected into an EDF, the erbium atoms absorb the pump light, which pushes the erbium atoms into excited states. When stimulated by light streams, for example an input optical signal having one or more wavelengths in a C-band (1528-1570 nm) or an L band (1570-1620 nm), the excited atoms return to a ground or lower state by stimulated emission. The stimulated emission has the same wavelength as that of the stimulating light. Therefore, the optical signal is amplified as it is propagating through the EDF. Furthermore, the EDF typically amplifies the entire optical signal regardless of wavelength.